1. Field of the Invention
The present invention relates to a dot measurement method and apparatus, and more particularly to technology for measuring positions and diameters of deposited dots formed by droplets ejected from a liquid ejection head, typically, an inkjet head, or for measuring the volume of the ejected liquid droplets.
2. Description of the Related Art
Japanese Patent Application Publication No. 2006-284406 proposes technology for determining deposition position displacement of dots formed by droplets ejected from a liquid ejection head. According to Japanese Patent Application Publication No. 2006-284406, the positions of isolated dots are measured by ejecting droplets to form isolated dots from the nozzles of a head, capturing an image of the droplet ejection result, calculating the straight line (path) traced by the respective dots, and then comparing with a reference straight line.
Japanese Patent Application Publication No. 10-230593 discloses technology for determining the ejection volume from nozzles, by forming a line pattern by means of ink and reading in the whole of the line pattern by means of an imaging element, and consequently calculating the density (integrated density) on a certain surface area and determining the ejection volume of the ink used in the line pattern on the basis of the density thus calculated.
However, the technology described in Japanese Patent Application Publication No. 2006-284406 is aimed at measuring the positions of isolated dots that are formed by droplets ejected from respective nozzles and are not connected with the other dots, and therefore the imaging apparatus (image reading apparatus) which reads in the isolated dots is required to have extremely high resolution corresponding to the dot diameter. More specifically, an imaging resolution which is approximately the same as the measurement accuracy of the isolated dots (for example, an accuracy of the order of 1 μm or less) is required, or alternatively, imaging has to be carried out at a high resolution which allows the edge of one dot to be captured clearly. Furthermore, the technology described in Japanese Patent Application Publication No. 2006-284406 principally calculates the dot deposition positions (dot positions), and cannot simultaneously calculate the dot diameter.
On the other hand, the technology described in Japanese Patent Application Publication No. 10-230593 is aimed at measuring the ink ejection volume, and cannot simultaneously measure the deposition positions of the dots formed by droplets ejected from the nozzles.